Hemoptysis refers to bleeding in a part of the lower respiratory tract, which is coughed out of the body. It is mainly caused by tuberculosis, lung cancer, severe pneumonia and bronchial dilatation. When there is tuberculosis, it is easy to be accompanied by coughing, coughing up sputum, blood in sputum, low fever, generalized weakness and night sweating, etc. The diagnosis can be confirmed by tuberculin test and sputum examination. If it is caused by lung cancer, it will cause metallic cough with blood in sputum, or there may be a lot of hemoptysis, usually need to do CT examination of lungs and also need to do the examination of tumor markers. In the presence of severe pneumonia, there will be fever, cough, hemoptysis. Bronchiectasis usually has a longer course, with coughing up large amounts of thick sputum and recurrent hemoptysis.